As a Bidder, you are able to check out through your "Item(s) Won Email Notification" OR through your Bidder account. 

If you did not receive your winning notification please check your SPAM folder, otherwise, you can access your Bidder account to check out at any time via BiddingOwl.com > Bidder Sign In > click on any one of the shopping carts next to your items ready for checkout > complete the checkout process.